The goal is to create some kind of programming language that hopefully makes game development for the SNES (from scratch) a little less painful than it usually is.
Does this generate fast assembly? Probably not that fast. This assembler uses some idioms (such as local variables on the stack) which are slow by the standards of the 65816. Generally, you will be able to write faster assembly than this compiler can output. But that's not the point. The point is that you don't have to write the assembly. You can focus on the algorithms and the bigger picture of your project. That's the whole point of a programming language, you know.
In any case, if it's too slow, even for Fast ROM, then we'll just cheat and use SA-1.